With miniaturization of electric equipment, development of small and lightweight or thin electronic components such as integrated circuits, wiring materials, or electronic substrates (hereinafter, comprehensively referred to as electronic components in some cases) have been conducted. As techniques that meet to the demand, recently, attention has been drawn to Printed Electronics.
Printed Electronics is a technical field in which various inks blended with a conductive component, a semiconductor component, or the like (hereinafter, various inks to be used in Printed Electronics are simply referred to as inks in some cases) are printed on the surfaces of substrates such as films or fabrics (for example, non-woven fabrics, woven fabrics, or knitted fabrics) to form various electronic components on the surfaces of the substrates.
By using techniques relating to Printed Electronics, electronic components are formed on the surfaces of lightweight and thin substrates, such as films or fabrics, or flexible substrates so that small and lightweight or flexible electric equipment can be provided.
As a technique relating to Printed Electronics, JP 2009-117552 A (hereinafter, referred to as Patent Document 1) discloses a suction stage in which a case where a solar cell element is processed to a film substrate having a size of about 1 m square is illustrated as an example. This technique relates to a suction stage for fixing a substrate by suctioning air, and it is disclosed that the substrate is fixed by suction to a stage base in a state where a flat plate having a plurality of rough pores passing through a space between a front surface and a rear surface and a laminate of sheet members in which fine pores are formed, such as a non-woven fabric, are interposed therebetween.
In this technique of Patent Document 1, the sheet member, which is provided with the flat plate having rough pores passing through a space between a front surface and a rear surface by mechanically processing a non-porous metallic material through cutting or the like and in which fine pores having air permeability are formed on the surface to which the substrate is fixed by suction, is attached to the suction stage of a vacuum suction apparatus that performs suction fixation of the substrate (see FIG. 1 or the like of Patent Document 1). In this technique, a non-woven fabric formed from a fluorine resin or the like is disclosed as a preferred embodiment of a sheet member having fine pores.
As another background art, JP 2012-61556 A (hereinafter, referred to as Patent Document 2) proposes a suction plate made of a non-woven fabric which is used in a suction surface (a suction stage provided with an intake port) of a vacuum suction apparatus that conveys or fixes paper, a film, a wafer, a glass plate, a metallic plate, or the like by vacuum suction. In this technique of Patent Document 2, focus is put on the influence on the surface of an object to be suctioned, and thus a non-woven fabric suction plate made of a thermally adhesive non-woven fabric is disclosed which satisfies a predetermined air permeation volume as compared to a sponge with poor abrasion resistance, or a porous sheet, sintered metal, and porous ceramics which are generally poor in air permeability and are poor in adhesion force with the substrate. Specifically, the plate is produced in such a structure that a thermally adhesive non-woven fabric A containing low-melting-point fibers as main components (mass per unit area: 50 to 200 g/m2, bulk density: 0.60 to 1.20 g/m3) and a non-woven fabric B containing, as main components, fibers having a higher melting point than that of the low-melting-point fibers by 70° C. or higher (mass per unit area: 300 to 800 g/m2, bulk density: 0.10 to 0.50 g/m3) are laminated and then the outer circumference of this laminate is fused by heat pressing. When the air permeation volume of the non-fused portion of this plate is adjusted to 50 to 150 cc/cm2/sec and the air permeation volume of the fused portion is adjusted to 5 cc/cm2/sec, the fused portion provided at the outer circumference facilitates the installation to the vacuum suction apparatus and a decrease in suction force caused by leakage of air from a portion other than the non-fused portion may be prevented. It is described that, with such a configuration, a suction plate can be provided in which evaluation is conducted using the air permeation volume and flatness determined by visual inspection or the like as indices, and which enables a workpiece to be strongly gripped and fixed and move and is applicable to a suction surface of the vacuum suction apparatus such as a hand portion of a robot.
Further, in the technique of Patent Document 2, a thermally adhesive fiber is used in each non-woven fabric. For this reason, as a preferred embodiment of the non-woven fabric A coming into contact with the workpiece, the non-woven fabric A is configured by fibers on which interlacing and heat treatment can be performed after carding, and there is disclosed a modified polyester fiber, a modified nylon fiber, a polyolefin fiber having a core-in-sheath structure of polyethylene, polypropylene, or the like or in which a half of the fiber cross-section is polypropylene, or a composite fiber having a core-in-sheath structure of polyester/nylon or the like or a two-component fiber in which one half of the fiber cross-section is polypropylene and the other half is polyethylene. It is described that, in consideration of carding machine processability, the fibers to be used have a fineness of 1 to 70 dtex and a fiber length of 1 to 100 mm and a thermally adhesive component, which attaches fibers, of a low-melting-point fiber is preferably in a melting point range of 10 to 200° C.
These techniques of two documents are referred to as a so-called sheet-fed method, and printing is performed on one substrate. Meanwhile, JP 2004-351413 A (Patent Document 3) relates to a method of applying and drying a liquid and discloses a technique of suctioning an object on a porous circulating member such as a screen belt or a screen drum through vacuuming and applying a liquid on the object to dry the liquid at least to the touch. This technique discloses as follows. A liquid is applied on a surface of an object suctioned and stably held on a circulating member, by which the object moves together with the circulating member without deforming. In addition, heat is transferred through the circulating member, which prevents the surface from skinning as is the case with a hot air furnace. Further, since a ununiformity of temperature control caused by heating technique is less likely to be affected, a high-quality coating film and a product thereof can be provided. Moreover, it is disclosed that a screen belt or screen drum of 40 mesh or more (hereinafter, comprehensively referred to as a screen drum in this application) can be used as an embodiment of the circulating member, and as necessary, air-permeability natural or fossil woven fabric or non-woven fabric, Japanese paper, synthetic paper, a plastic film, or the like may be supplied thereon in an underlying web of a single layer form or a multi-layer form to suction the object. It is described that the underlying web is used for preventing the surface of the circulating member from contamination and allowing recovery of the scattered liquid (printing material). As another effect of the document, it is mentioned to indirectly processing for the object, so that the problem on a small gap at the seam portion of the screen belt or drum can be solved.
As understood from the background arts of the aforementioned Patent Document 1 and Patent Document 2, the vacuum suction apparatus has been widely used for fixing and conveying the workpiece. Particularly, for forming an electronic component or the like to a substrate used in the field of Printed Electronics (hereinafter, in the present application, a film with substantially no air permeability is comprehensively referred to as an “air-impermeable substrate”), the suction stage surface, which forms the contact face with the substrate, of the vacuum suction apparatus is demanded to have flatness of a surface to be printed with extremely high accuracy in printing of an ink as well as to enable immobilization of the air-impermeable substrate. As such an air-impermeable substrate, a polyimide film or polyester film having a thickness of about 50 μm is currently being put to practical use. However, as the thinning is being advanced, and as also disclosed in the aforementioned Patent Document 1, according to an increase in size of a film substrate itself to be fixed, it is difficult to maintain the flatness of the film itself in a state of being suctioned by the suction stage. Thus, highly accurate flatness is also demanded for an air-permeable sheet, which is interposed between the suction stage and the substrate, at the time of printing.